Welcome to the forum @Aster
Please export the nodes in your simple flow and paste the flow here. Also tell us if you have installed any extra nodes. In order to make flow usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```
)
```
code goes here
```
See this post for more details - How to share code or flow json
Also, if you are a beginner with node-red then I recommend watching this playlist: Node-RED Essentials. The videos are done by the developers of node-red. They're nice & short and to the point. You will understand a whole lot more in about 1 hour. A small investment for a lot of gain.